The present invention relates to compositions for external use having a melanin synthesis-inhibiting activity, which can be formulated in cosmetic compositions or ointments to exhibit a human skin-whitening effect and anti-suntan effect.
It is known that kojic acid and its ester have an effect to inhibit synthesis of melanin (Japanese Tokkyo Kokai Nos. 18739/1978, 7776/1981, 79616/1981, 33207/1984).
Kojic acid or its esters have an action to inhibit an activity of tyrosinase which is the enzyme to convert tyrosine to dopa, then to dopa quinone in the pathway of melanin synthesis, whereby the synthesis of melanin is prevented.
The present inventor has intensively studied the kojic acid or its esters, in order to obtain more effective melanin synthesis-inhibiting activity, by producing various derivatives of kojic acid or its esters or by using with other drugs. As a result of the study, it has been found a surprising fact that the melanin synthesis can be synergistically inhibited by blending the particular compounds with kojic acid or its esters, and then the present invention has been completed.